#include<fstream>
using namespace std;
ifstream f("energii.in");
ofstream g("energii.out");
int n, i, e, j, d[10001][10001];
pair<int, int> a[10001];
int main()
{
    f>>n>>e;
    //for(i=0;i<=n;i++)
        for(j=0;j<=e;j++)
            d[i][j]=2000000000;
    for(i=1;i<=n;i++)
        f>>a[i].first>>a[i].second;
    for(i=1;i<=n;i++)
        for(j=1;j<=e;j++)
        {
            d[i][j]=2000000000;
            if(j>=a[i].first)
                d[i][j]=min(d[i-1][j], d[i-1][j-a[i].first]+a[i].second);
            else d[i][j]=min(d[i-1][j], a[i].second);
        }
    if(d[n][e]!=2000000000)
        g<<d[n][e];
    else g<<"-1";
    return 0;
}